Electrophotographic photoreceptor containing hydrazone compounds

ABSTRACT

An electrophotographic photoreceptor comprising an electrically conductive support and a photosensitive layer formed thereon, wherein said photosensitive layer contains at least one member selected from the group consisting of hydrazone compounds of the formulas (I), (II) and (III): ##STR1## wherein X is a hydrogen atom or a group of the formula (IV): 
     
         --C(R.sup.8)═N--Q.sup.2                                (IV) 
    
     Q 1  is a group of the formula (V), (VI), (VII), (VIII) or (IX); Q 2  is a group of the formula (VI), (VII), (VIII), (IX) or (X); each of Q 3  and Q 4  which may be the same or different, is a group of the formula (VI), (VII), (VIII), (IX) or (XI): ##STR2##

This invention relates to an electrophotographic photoreceptor. Moreparticularly, it relates to a highly sensitive electrophotographicphotoreceptor having a photosensitive layer comprising an organicphotoconductive material.

Heretofore, inorganic photoconductive materials such as selenium,cadmium sulfide and zinc oxide have been widely used in thephotosensitive layers of the electrophotographic photoreceptors.However, selenium and cadmium sulfide are required to be recovered astoxic substances. Further, selenium is crystallized by heat and thus isinferior in the heat resistance. Cadmium sulfide and zinc oxide areinferior in the moisture resistance. Zinc oxide has a drawback that itis poor in the printing resistance. Under these circumstances, researchefforts are still being made to develop novel photosensitive materials.Recently, studies on use of organic photoconductive materials for thephotosensitive layers of the electrophotographic photoreceptors havebeen advanced, and some of them have materialized into practical use.The organic photoconductive materials have many advantages over theinorganic materials. For example, they are light in weight and easy tofabricate into films, and they can be easily manufactured intophotoreceptors or into transparent photoreceptors depending upon thecertain kinds of the material.

Recently, the current research activities are directed to so-calledfunction-separated photoreceptors whereby functions of generating andtransporting electric charge carriers are performed by separatecompounds, since they are effective for high sensitivity, and organicphotoreceptors of this type have been practically employed.

As a carrier transporting material, a polymer-type photoconductivecompound such as polyvinyl carbazole may be employed. Otherwise, a lowmolecular weight photoconductive compound may be used as dispersed ordissolved in a binder polymer.

Particularly in the case of an organic low molecular weightphotoconductive compound, it is possible to select as a binder a polymerexcellent in the film-forming property, flexibility and adhesiveproperty, whereby a photoreceptor excellent in the mechanical propertiescan readily be obtained (e.g. Japanese Unexamined Patent PublicationsNo. 196767/1985, No. 218652/1985, No. 233156/1985, No. 48552/1988 andNo. 267552/1989). However, it has been difficult to find a suitablecompound for the preparation of a highly sensitive photoreceptor.

The present inventors have conducted extensive researches for organiclow molecular weight photoconductive compounds capable of presentingelectrophotographic photoreceptors having high sensitivity and highdurability and as a result, have found that certain specific hydrazonecompounds are suitable for this purpose. The present invention has beenaccomplished on the basis of this discovery.

Thus, the present invention provides an electrophotographicphotoreceptor comprising an electrically conductive support and aphotosensitive layer formed thereon, wherein said photosensitive layercontains at least one member selected from the group consisting ofhydrazone compounds of the formulas (I), (II) and (III): ##STR3##wherein X is a hydrogen atom or a group of the formula (IV):

    --C(R.sup.8)═N--Q.sup.2                                (IV)

Q¹ is a group of the formula (V), (VI), (VII), (VIII) or (IX); Q² is agroup of the formula (VI), (VII), (VIII), (IX) or (X); each of Q³ and Q⁴which may be the same or different, is a group of the formula (VI),(VII), (VIII), (IX) or (XI): ##STR4##

Y is a bivalent hydrocarbon group which may have substituents, A is analiphatic linking group which may have substituents, where the mainchain of the linking group may contain an oxygen atom or a carbon-carbondouble bond; in the case where the main chain of the linking group iscomposed of only carbon atoms, the constituting carbon number is from 3to 5; and in the case where the oxygen atom is contained, theconstituting carbon-carbon chain length has the carbon number of from 2to 5; each of Ar¹ and Ar² which may be the same or different, is an arylgroup which may have substituents or a heterocyclic group; each of R¹,R², R³, R⁴, R⁵, R⁹, R¹⁵, R¹⁶ and R¹⁹ which may be the same or different,is a hydrogen atom, a lower alkyl group which may have substituents, ahalogen atom or a lower alkoxy group which may have substituents; eachof R⁶, R⁸, R¹⁷ and R¹⁸ which may be the same or different, is a hydrogenatom, a methyl group or a phenyl group which may have substituents; eachof R⁷ and R¹⁰ is an aryl group which may have substituents in theformula (I), or an aryl group which may have substituents or aheterocyclic group in the formula (II); each of R¹¹, R¹², R¹³ and R¹⁴which may be the same or different, is an alkyl group which may havesubstituents, an aralkyl group which may have substituents; an arylgroup which may have substituents, a vinyl group which may havesubstituents, or an allyl group; and R²⁰ is an aryl group which may havesubstituents; or a heterocyclic group.

In the accompanying drawings, FIG. 1 is an infrared absorption spectrumof the monohydrazone compound obtained in Preparation Example 2.

FIG. 2 is an infrared absorption spectrum of the dihydrazone compoundobtained in Preparation Example 3.

FIG. 3 is an infrared absorption spectrum of the monohydrazone compoundobtained in Preparation Example 5.

FIG. 4 is an infrared absorption spectrum of the dihydrazone compoundobtained in Preparation Example 6.

FIG. 5 is an infrared absorption spectrum of the dihydrazone compoundobtained in Preparation Example 8.

Now, the present invention will be described in detail with reference tothe preferred embodiments.

The electrophotographic photoreceptor of the present invention containsat least one member selected from the group consisting of hydrazonecompounds of the formulas (I), (II) and (III) in the photosensitivelayer.

In the formula (I), (II) or (III), X is an hydrogen atom or a group ofthe formula (IV):

    --C(R.sup.8)═N--Q.sup.2                                (IV)

Q¹ is a group of the formula (V), (VI), (VII), (VIII) or (IX); Q² is agroup of the formula (VI), (VII), (VIII), (IX) or (X); each of Q³ and Q⁴which may be the same or different, is a group of the formula (VI),(VII), (VIII), (IX) or (XI): ##STR5##

Y is a bivalent hydrocarbon group, for example, a methylene group, apropylene group, a xylylene group, a cyclohexylene group, a vinylenegroup or a phenylene group which may have substituents such as a halogenatom, a hydroxyl atom, a saturated or unsaturated hydrocarbon group, analkoxy group, an aryloxy group, a dialkylamino group or a diarylaminogroup.

A is an aliphatic linking group which may have substituents, forexample, a lower alkyl group such as a methyl group or an ethyl group, alower alkoxy group such as a methoxy group or an ethoxy group, a halogenatom such as a chlorine atom or a bromine atom or an aryl group such asa phenyl group or a naphthyl group. In the case where the main chain ofthe linking group is composed of only carbon atoms, the constitutingcarbon number is preferably from 3 to 5 in view of the improvement ofsolubility in a solvent.

In the case where the main chain of the linking group contains theoxygen atom, the main chain has the form of an ether linkage and theconstituting carbon-carbon chain length has the carbon number of from 2to 5.

Each of Ar¹ and Ar² which may be the same or different, is an aryl groupsuch as a phenyl group or a naphthyl group which may be substituted by alower alkyl group such as a methyl group or an ethyl group, a loweralkoxy group such as a methoxy group or an ethoxy group or a phenylgroup; or a heterocyclic group such as a pyrrolyl group, a thiophenylgroup, a furyl group or a carbazolyl group which may be substituted bythe same substituents as the above.

Each of R¹, R², R³, R⁴, R⁵, R⁹, R¹⁵, R¹⁶ and R¹⁹ which may be the sameor different, is a hydrogen atom; a halogen atom such as a chlorineatom, a bromine atom or an iodine atom; a lower alkyl group such as amethyl group or an ethyl group; or a lower alkoxy group such as amethoxy group or an ethoxy group. Each of the lower alkyl group and thelower alkoxy group may have substituents.

Each of R⁶, R⁸, R¹⁷ and R¹⁸ which may be the same or different, is ahydrogen atom; a methyl group; a phenyl group; or a substituted phenylgroup such as a tolyl group, an anisyl group or a chlorophenyl group.

In the formula (I), each of R⁷ and R¹⁰ which may be the same ordifferent, is a phenyl group; or an aryl group which may havesubstituents, such as a tolyl group, an anisyl group or a chlorophenylgroup.

In the formula (II), each of R⁷ and R¹⁰ which may be the same ordifferent, is a phenyl group; an aryl group which may have substituents,such as a tolyl group, an anisyl group or a chlorophenyl group; or aheterocyclic group such as a pyrrolyl group, a thiophenyl group, a furylgroup or a carbazolyl group.

Each of R¹¹, R¹², R¹³ and R¹⁴ which may be the same or different, is analkyl group such as a methyl group, an ethyl group, a propyl group, abutyl group or a hexyl group; an aralkyl group such as a benzyl group, anaphthylmethyl group or a phenethyl group; an aryl group such as aphenyl group or a naphthyl group; a vinyl group; or an allyl group. Eachof the alkyl group, the aralkyl group, the aryl group and the vinylgroup may be substituted with a lower alkyl group such as a methyl groupor an ethyl group, a lower alkoxy group such as a methoxy group or anethoxy group, or a phenyl group.

R²⁰ is a phenyl group; an aryl group which may have substituents, suchas a tolyl group, an anisyl group or a chlorophenyl group; or aheterocyclic group such as a pyrrolyl group, a thiophenyl group, a furylgroup or a carbazolyl group.

Typical examples of the arylamine hydrazone compound of the formula (I)are given hereinbelow. However, the arylamine hydrazone compound usefulin the present invention is by no means limited to the typical examplesso long as it does not exceed the gist of the present invention.##STR6##

Typical examples of the the arylamine hydrazone compound of the formula(II) are given hereinafter. However, the arylamine hydrazone compounduseful in the present invention is by no means limited to these typicalexamples so long as it does not exceed the gist of the presentinvention. ##STR7##

Typical examples of the dihydrazone compound of the formula (III) aregiven hereinafter. However, the dihydrazone compound useful in thepresent invention is by no means limited to these typical examples solong as it does not exceed the gist of the present invention. ##STR8##

The arylamine hydrazone compound of the formula (I) can be produced by aknown method.

For example, a method may be mentioned wherein an arylamine compound asa starting material is subjected to a known formylation or acylationreaction and then dehydration with a desired hydrazine to obtain adesired compound.

(A-1)

In a case where each R⁶ and R⁸ in the formula (I) is a hydrogen atom, anarylamine compound of the formula (XII) is reacted with a formylatingagent such as N,N-dimethylformamide or N-methylformanilide as shownbelow: ##STR9## (in the formulas (XII) and (XIII), R¹, R², R³, R⁴, Ar¹,Ar² and Y are as defined with respect to the formula (I), and in theformula (XIII), Z is a hydrogen atom or --CHO) in the presence ofphosphorous oxychloride to obtain an aldehyde of the formula (XIII).(Vilsmeyer reaction)

It is possible to use a large excess amount of the formylating agent asa reaction solvent. It is also possible to use a solvent which is inertto the reaction, such as o-dichlorobenzene or benzene.

(A-2)

The compound of the formula (XIII) thus obtained is then subjected todehydration condensation with a hydrazine of the formula (XIVa) or(XIVb) to produce an arylamine hydrazine of the formula (I).

R⁷ and R⁵ of the formula (XIVa) or R⁹ and R¹⁰ of the formula (XIVb) mayform a heterocyclic ring containing a nitrogen atom, of the formula(VI), (VII), (VIII) or (IX). ##STR10##

The dehydration condensation may be conducted, if necessary, underheating at 50° C. to 150° C., in a solvent inert to the reaction, suchas methanol, ethanol, tetrahydrofuran, cellosolve,N,N-dimethylformamide, benzene or toluene. As occasion demands, an aidsuch as paratoluene sulfonic acid, hydrochloric acid or sodium acetatemay be employed as a reaction accelerator.

Condensation reaction

The compounds of the formulas (XIVa) and (XIVb) may be used singly or asa mixture thereof, or may be reacted stepwise as the case may be.

(B-1)

In a case where each of R⁶ and R⁸ in the formula (I) is not a hydrogenatom, an arylamine compound of the formula (XII) is reacted with an acidchloride of the formula: Cl--CO--R⁶ or Cl--CO--R⁸, as shown below:##STR11## (R¹, R², R³, R⁴, Ar¹, Ar² and Y in the formula (XV) are asdefined with respect to the formula (I), and in the formula (XV), W is ahydrogen atom or --C(R⁸)═O, and R⁶ and R⁸ which may be the same ordifferent, are as defined with respect to the formula (I)) in thepresence of a Lewis acid such as aluminium chloride, iron chloride orzinc chloride, in a solvent such as nitrobenzene, dichloromethane orcarbon tetrachloride to obtain a ketone of the formula (XV).

R⁶ and R⁸ may be the same or different. When R⁶ and R⁸ are not the same,the reaction may be conducted by mixing or stepwise adding the acidchloride to be added.

(B-2)

This method can be accomplished by the same reaction as (A-2).

In these reactions, if necessary, it is possible to obtain highlypurified products by a known purification such as recrystallization,sublimation or column chromatography after completion of each step orafter completion of all steps.

The arylamine hydrazone compound of the formula (II) can be produced bya known method.

For example, a method may be mentioned wherein an arylamine compound asa starting material is subjected to a known formylation or acylationreaction and then subjected to dehydration with a desired hydrazine toobtain a desired compound.

(A-3)

In a case where each of R⁶ and R⁸ in the formula (II) is a hydrogenatom, an arylamine compound of the formula (XVI) is reacted with aformylating agent such as N,N-dimethylformamide or N-methylformanilideas shown below: ##STR12## (R¹, R², R³, R⁴, Ar¹, Ar² and A in theformulas (XVI) and (XVII) are as defined with respect to the formula(II) and Z in the formula (XVII) is a hydrogen atom or --CHO) in thepresence of phosphorous oxychloride to obtain an aldehyde of the formula(XVII)). (Vilsmeyer reaction)

It is possible to use a large excess amount of the formylating agent asa reaction solvent. It is also possible to use a solvent which is inertto the reaction, such as o-dichlorobenzene or benzene.

(A-4)

Then, the compound of the formula (XVII) thus obtained is dehydrativelycondensated with a hydrazine of the formula (XVIIIa) or (XVIIIb) asshown below to produce an arylamine hydrazine of the formula (II).

Here, R⁷ and R⁵ of the formula (XVIIIa) or R⁹ and R¹⁰ of the formula(XVIIIb) may form a heterocyclic ring of the formula (VI), (VII), (VIII)or (IX), which contains a nitrogen atom. ##STR13##

The dehydration-condensation may, if necessary, be conducted in asolvent inert to the reaction, such as methanol, ethanol,tetrahydrofuran, cellosolve, N,N-dimethylformamide, benzene or toluene,under heating at from 50° C. to 150° C. As occasion demands, an aid suchas paratoluene sulfonic acid, hydrochloric acid or sodium acetate may beused as a reaction accelerator.

Condensation reaction

The compounds of the formulas (XVIIIa) and (XVIIIb) may be employedsingly or as a mixture, or may be reacted stepwise as the case may be.

(B-3)

In the case where each of R⁶ and R⁸ of the formula (I) is not a hydrogenatom, the arylamine compound of the formula (XVI) is reacted with anacid chloride of the formula: Cl--CO--R⁶ or Cl--CO--R⁸, as shown below:##STR14## (in the formula (XIX), R¹, R², R³, R⁴, Ar¹, Ar² and A are asdefined with respect to the formula (II), W is a hydrogen atom or--C(R⁸)═O, and R⁶ and R⁸ which may be the same or different, are asdefined with respect to the formula (II)) in a solvent such asnitrobenzene, dichloromethane or carbon tetrachloride, in the presenceof a Lewis acid such as aluminium chloride, iron chloride or zincchloride to obtain a ketone of the formula (XIX).

R⁶ and R⁸ may be the same or different. In the case where R⁶ and R⁸ aredifferent, the reaction may be conducted by mixing the acid chloride tobe added or adding it stepwise.

(B-4)

This method can be accomplished by the same reaction as (A-4).

In these reactions, if necessary, it is possible to obtain highlypurified products by a known purification method such asrecrystallization, sublimation or column chromatography after completionof each step or after completion of all steps.

The dihydrazone compound of the formula (III) can be produced by a knownmethod.

For example, a method may be mentioned, wherein a diamine compound as astarting material is subjected to a known carbonyl-introduction reactionand then to dehydration with a desired hydrazine to obtain a desiredcompound.

(A-5)

In the case where each of R⁷ and R⁸ of the formula (III) is a hydrogenatom, a diamine compound of the formula (XX) is reacted with aformylating agent such as N,N-dimethylformamide or N-methylformanilideas shown below: ##STR15## (Y, R¹¹, R¹², R¹³, R¹⁴, R¹⁵ and R¹⁶ of theformulas (XX) and (XXI) are as defined with respect to the formula(III)) in the presence of phosphorous oxychloride to obtain a dialdehydeof the formula (XXI). (Vilsmeyer reaction)

It is possible to employ a large excess amount of the formylating agentas a reaction solvent. It is also possible to employ a solvent inert tothe reaction, such as o-dichlorobenzene or benzene.

(A-6)

Then, the compound of the formula (XXI) thus obtained is dehydrativelycondensated with a hydrazine of the formula: H₂ N--Q³ or H₂ N--Q⁴, whereQ³ and Q⁴ are as defined with respect to the formula (III), to produce adihydrazone of the formula (III) as shown below: ##STR16##

The dehydratively condensation may be, if necessary, conducted underheating at from 50° C. to 150° C., in a solvent inert to the reaction,such as methanol, ethanol, tetrahydrofuran, cellosolve,N,N-dimethylformamide, benzene or toluene. As occasion demands, an aidsuch as paratoluene sulfonic acid, hydrochloric acid or sodium acetatemay be employed as a reaction accelerator.

Hydrazonization

Q³ and Q⁴ may be the same or different. In the case where Q³ and Q⁴ aredifferent, the reaction may be conducted by mixing a hydrazine to beadded or adding it stepwise.

(B-5)

In the case where each of R⁷ and R⁸ in the formula (III) is not ahydrogen atom, a diamine compound of the formula (XX) is reacted with anacid chloride of the formula: Cl--CO--R¹⁷ or Cl--CO--R¹⁸, as shownbelow: ##STR17## (Y, R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷ and R¹⁸ in theformulas (XXI) and (XXII) are as defined with respect to the formula(III)) in the presence of a Lewis acid such as aluminium chloride, ironchloride or zinc chloride in a solvent such as nitrobenzene,dichloromethane or carbon tetrachloride to obtain a diketone of theformula (XXII).

R¹⁷ and R¹⁸ may be the same or different. In the case where R¹⁷ and R¹⁸are different, the reaction may be conducted by mixing the acid chlorideto be added or adding it stepwise.

(B-6)

This reaction can be conducted by the same reaction as (A-6).

It is possible to obtain highly purified products by a knownpurification method such as recrystallization, sublimation or columnchromatography, after completion of each step or after completion of allsteps.

The electrophotographic photoreceptor of the present invention has aphotosensitive layer containing at least one member selected from thegroup consisting of the hydrazone compounds of the formulas (I), (II)and (III).

The hydrazone compound of the formula (I), (II) or (III) exhibitsexcellent properties as an organic photoconductive material. Especiallywhen used as a carrier transport material, it gives a photoreceptorhaving high sensitivity and excellent durability.

Various types are known for the photosensitive layer for anelectrophotographic photoreceptor. The photosensitive layer of theelectrophotographic photoreceptor of the present invention may be anyone of such types. For example, the following types may be mentioned:

(i) a photosensitive layer having the hydrazone compound and, asoccasion demands, a pigment useful as a sensitizing agent and a carrierattracting compound added in a binder.

(ii) a photosensitive layer having photoconductive particles capable ofgenerating an electric charge carrier at an extremely high efficiencyupon absorption of light and the hydrazone compound added in a binder.

(iii) a photosensitive layer having laminated a carrier transport layercomposed of the hydrazone compound and a binder and a carrier generationlayer composed of photoconductive particles capable of generating anelectric charge carrier at an extremely high efficiency upon absorptionof light, or composed of such photoconductive particles and a binder.

In such a photosensitive layer, a known other hydrazone compound orstilbene compound having excellent properties as an organicphotoconductive material, may be incorporated together with at least onemember selected from the group consisting of the hydrazone compounds ofthe formulas (I), (II) and (III).

In the present invention, when at least one member selected from thegroup consisting of the hydrazone compounds of the formulas (I), (II)and (III) is used in a carrier transport layer of a photosensitive layerwhich comprises two layers of the carrier transport layer and a carriergeneration layer, it is possible to obtain a photoreceptor havingparticularly high sensitivity and low residual potential and which hasexcellent durability such that even when used repeatedly, the change inthe surface potential, the deterioration of the sensitivity or theaccumulation of the residual potential is small.

The electrophotographic photoreceptor of the present invention can beprepared in accordance with a usual method by dissolving at least onemember selected from the group consisting of the hydrazone compounds ofthe formulas (I), (II) and (III) together with the binder in a suitablesolvent, adding photoconductive particles capable of generating anelectric charge carrier at an extremely high efficiency upon absorptionof light, a sensitizing dye, an electron attracting compound, aplasticizer, a pigment or other additives, as the case requires, toobtain a coating solution, and then applying such a coating solution onan electrically conductive support, followed by drying to form aphotosensitive layer having a thickness of from a few μm to a few tensμm. The photosensitive layer comprising two layers of the carriergeneration layer and the carrier transport layer can be prepared eitherby applying the above mentioned coating solution on the carriergeneration layer, or forming a carrier generation layer on the carriertransport layer obtained by coating the above mentioned coating solution

The solvent useful for the preparation of the coating solution is asolvent capable of dissolving the hydrazone compound, for example, anether such as tetrahydrofuran or 1,4-dioxane; a ketone such as methylethyl ketone or cyclohexanone; an aromatic hydrocarbon such as tolueneor xylene; an aprotic polar solvent such as N,N-dimethylformamide,acetonitrile, N-methyl pyrrolidone or dimethyl sulfoxide; an ester suchas ethyl acetate, methyl formate or methyl cellosolve acetate; or achlorinated hydrocarbon such as dichloroethane or chloroform. It is ofcourse necessary to select among them the one capable of dissolving thebinder. The binder may be a polymer or copolymer of a vinyl compoundsuch as styrene, vinyl acetate, vinyl chloride, an acrylate, amethacrylate or butadiene, or various polymers compatible with a styrenecompound, such as polyvinyl acetal, polycarbonate, polyester,polysulfone, polyphenyleneoxide, polyurethane, cellulose ester,cellulose ether, a phenoxy resin, a silicone resin and an epoxy resin.The binder is used usually in an amount within a range of from 0.5 to 30times by weight, preferably from 0.7 to 10 times by weight, relative tothe hydrazone compound.

The photoconductive particles, dyes, pigments or electron attractingcompounds to be added to the photosensitive layer may be those wellknown in the art. The photoconductive particles capable of generatingelectron charge carriers at an extremely high efficiency upon absorptionof light, include inorganic photoconductive particles such as selenium,selenium-tellurium alloy, selenium-arsenic alloy and a cadmium sulfideand amorphous silicon; and organic photoconductive particles such asmetal-containing phthalocyanine, perinone dyes, thioindigo dyes,quinacridone, perylene dyes, anthraquinone dyes, azo dyes, bisazo dyes,trisazo dyes, tetrakisazo dyes and cyanine dyes. (Particularly, aphotoreceptor having an improved sensitivity against laser beam, can beobtained by combining with the metal-containing phthalocyanine.) Thedyes include, for example, triphenylmethane dyes such as Methyl Violet,Brilliant Green and Crystal Violet; thiazine dyes such as MethyleneBlue; quinone dyes such as quinizarin and cyanine dyes as well aspyrylium salts, thiapyrylium salts and benzopyrylium salts. The electronattracting compound capable of forming a carrier transport complextogether with the hydrazone compound, includes, for example, quinonessuch as chloranil, 2,3-dichloro-1,4-naphthoquinone,1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone,2-chloroanthraquinone and phenanthrenequinone; aldehydes such as4-nitrobenzaldehyde; ketones such as 9-benzoylanthracene, indanedione,3,5-dinitrobenzophenone, 2,4,7-trinitrofluorenone,2,4,5,7-tetranitrofluorenone and 3,3',5,5'-tetranitrobenzophenone; acidanhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride;cyano compounds such as tetracyanoethylene, terephthalal malononitrile,9-anthrylmethylidene malononitrile, 4-nitrobenzal malononitrile and4-(p-nitrobenzoyloxy)benzal malononitrile; and phthalides such as3-benzalphthalide, 3-(α-cyano-p-nitrobenzal)phthalide and3-(α-cyano-p-nitrobenzal)-4,5,6,7-tetrachlorophthalide.

Further, the photosensitive layer of the electorphographic photoreceptoraccording to this invention may contain a well-known plasticizer for theimprovement of the film-forming properties, flexibility and mechanicalstrength. The plasticizer to be added to the above coating solution forthis purpose may be a phthalic ester, a phosphoric ester, an epoxycompound, a chlorinated paraffin, a chlorinated fatty acid ester or anaromatic compound such as methylnaphthalene. In a case where thehydrazone compound is used as a carrier transport material in thecarrier transport layer, the coating solution may be of the abovedescribed composition, but photoconductive particles, dyes, pigments,electron attracting compounds and the like may be eliminated or added ina small amount. The carrier generation layer in this case includes alayer prepared by forming the above mentioned photoconductive particlesinto a film by means of e.g. vapor deposition, and a thin layer preparedby applying a coating solution which is obtained by dissolving ordispersing the photoconductive particles and optionally a binder polymeras well as an organic photoconductive material, a dye and an electronattracting compound in a solvent, and drying it.

The photoreceptor thus formed may further have an adhesive layer, anintermediate layer, a transparent insulation layer or the like, as thecase requires. As the electrically conductive support on which thephotosensitive layer is formed, any material which is commonly used forelectrophotographic photoreceptors, can be employed. Specifically, adrum or sheet of a metal such as aluminum, stainless steel or copper, ora laminate of foils of such metals, or a vapor-deposition product ofsuch metals, may be mentioned. Further, a plastic film, a plastic drum,paper or a paper tube electrified by coating a conductive material suchas metal powder, carbon black, copper iodide or a polymer electrolytetogether with an appropriate binder, may be mentioned. Further, anelectrically conductive plastic sheet or drum containing a conductivesubstance such as metal powder, carbon black or carbon fiber, may bementioned.

The electrophotographic photoreceptor of the present invention has avery high sensitivity and a small residual potential which is likely tocause fogging, and it has a feature of excellent durability since theaccumulation of the residual potential due to repeated use andfluctuations in the surface potential and in the sensitivity are minimumas the light-fatigue is minimum.

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted by such specific Examples. In theExamples, "parts" means "parts by weight".

PREPARATION EXAMPLE 1

1.5 g of bis(p-diphenylaminophenoxy)methane: ##STR18## was dissolved in30 ml of N,N-dimethylformamide, and 0.64 ml of phosphorous oxychloridewas added thereto, and then the reaction was conducted at 60° C. for 5hours. The reaction solution was left to cool, poured in 200 g of icewater, hydrolyzed with sodium hydroxide, and further subjected tofiltration and purification treatments by known methods to obtain 0.61 gof a monoformylated product as yellow oily products and 0.33 g of adiformylated product as yellow oily products.

These compounds were found to be compounds of the following formulas,respectively, from the following values of elemental analysis, the massspectrometric analysis and the infrared absorption spectrum analysis:

(1) Monoformylated compound

    ______________________________________                                        Elemental analysis:                                                           As C.sub.38 H.sub.30 N.sub.2 O.sub.3                                                     C %           H %    N %                                           ______________________________________                                        Calculated 81.12         5.37   4.98                                          Found      80.21         5.41   4.87                                          ______________________________________                                        Results of mass spectrometric analysis:                                       As C.sub.38 H.sub.30 N.sub.2 O.sub.3                                          ______________________________________                                        MW = 562                                                                      M.sup.+  = 562                                                                 ##STR19##                                                                    ______________________________________                                    

(2) Diformylated compound

    ______________________________________                                        Elemental analysis:                                                           As C.sub.39 H.sub.30 N.sub.2 O.sub.4                                                     C %           H %    N %                                           ______________________________________                                        Calculated 79.30         5.12   4.74                                          Found      79.21         5.21   4.80                                          ______________________________________                                        Results of mass spectrometric analysis:                                       As C.sub.39 H.sub.30 N.sub.2 O.sub.4                                          ______________________________________                                        MW = 590                                                                      M.sup.+  = 590                                                                 ##STR20##                                                                    ______________________________________                                    

PREPARATION EXAMPLE 2

0.61 g of the monoformyl compound synthesized in Preparation Example 1and 0.28 g of 1,1-diphenylhydrazine were reacted in the presence of anacetic acid catalyst in a mixed solution of 3 ml of tetrahydrofuran and5 ml of methanol at 50° to 60° C. for 2 hours. Then, the reactionsolution was poured in 500 ml of methanol and subjected to filtrationand purification treatments by known methods to obtain 0.79 g of ayellow solid.

This compound was found to be a monohydrazone compound of the followingformula (Exemplary Compound No. 1-1 as mentioned above) from thefollowing values of elemental analysis, the mass spectrometric analysisand the infrared absorption spectrum analysis (FIG. 1):

    ______________________________________                                        Elemental analysis:                                                           As C.sub.50 H.sub.40 N.sub.4 O.sub.2                                                     C %           H %    N %                                           ______________________________________                                        Calculated 82.39         5.53   7.69                                          Found      83.29         5.60   7.24                                          ______________________________________                                        Results of mass spectrometric analysis:                                       As C.sub.50 H.sub.40 N.sub.4 O.sub.2                                          ______________________________________                                        MW = 728,                                                                     M.sup.+  = 728                                                                 ##STR21##                                                                    ______________________________________                                    

PREPARATION EXAMPLE 3

0.33 g of the diformyl compound synthesized in Preparation Example 1 wasreacted with 0.29 g of 1,1-diphenylhydrazine in the presence of anacetic acid catalyst in a mixed solution of 3 ml of tetrahydrofuran and5 ml of methanol at 50° to 60° C. for 2 hours. Then, the reactionsolution was poured in 500 ml of methanol and subjected to filtrationand purification treatments by known methods to obtain 0.22 g of ayellow solid.

This compound was found to be a dihydrazone compound of the followingformula (Exemplary Compound No. 1-21 as mentioned above) from thefollowing values of elemental analysis and the infrared absorptionspectrum analysis (FIG. 2):

    __________________________________________________________________________    Elemental analysis:                                                           As C.sub.63 H.sub.50 N.sub.6 O.sub.2                                                       C %              H %                                                                              N %                                          __________________________________________________________________________           Calculated                                                                          81.97            5.46                                                                             9.10                                                Found 81.83            5.55                                                                             9.17                                         __________________________________________________________________________     ##STR22##                                                                    __________________________________________________________________________

EXAMPLE 1

1.0 part of a titanium oxyphthalocyanine dye and 0.5 part ofpolyvinylbutyral (Tradename: Polyvinylbutyral #6000, manufactured byDenki Kagaku Kogyo K. K.) were dispersed and pulverized in 30 parts of4-methoxy-4-methylpentanone-2 (manufactured by Mitsubishi KaseiCorporation).

This dispersion was coated by a wire bar on an aluminium layervapor-deposited on a polyester film having a thickness of 100 μm so thatthe weight after drying would be 0.2 g/m², followed by drying to form acarrier generation layer.

A coating solution prepared by dissolving 70 parts of the hydrazinecompound prepared in Preparation Example 3 and 100 parts of apolycarbonate as shown below in 900 parts of dioxane, was coated thereonand dried to form a carrier transport layer having a thickness of 17 μm.##STR23##

With respect to the electrophotographic photoreceptor having aphotosensitive layer comprising two layers thus obtained, thesensitivity i.e. the half-decay exposure intensity was measured andfound to be 2.7 (μW/cm²)⁻¹.

Here, the half-decay exposure intensity was determined by firstlycharging the photoreceptor in a dark place with corona discharge at -4.8KV, then subjecting to exposure to a light of 775 nm, and measuring theexposure intensity required until the surface potential decayed from 500V to 250 V.

EXAMPLE 2

A photoreceptor was produced in the same manner as in Example 1 exceptthat an unsymmetrical disazo dye of the following formula was usedinstead of the phthalocyanine dye used in Example 1, then subjected toexposure to incandescent light, and measuring the half-decay exposureintensity to find to be 1.0 lux.sec. ##STR24##

EXAMPLES 3 TO 17

Electrophotographic photoreceptors were produced in the same manner asin Example 1 except that hydrazone compounds as shown in Table 1,synthesized in the same manner as in Preparation Example 2 or 3, and thetitanium oxyphthalocyanine dye used in Example 1 was used for thecarrier generation layer, and their sensitivities are shown in thefollowing Table 1.

                  TABLE 1                                                         ______________________________________                                                                   Sensitivity                                        Example   Exemplary Compound No.                                                                         (μW/cm.sup.2).sup.-1                            ______________________________________                                        3         1-1              2.4                                                4         1-2              1.8                                                5         1-5              2.3                                                6         1-8              1.9                                                7         1-11             2.4                                                8         1-12             2.2                                                9         1-18             1.8                                                10        1-22             1.8                                                11        1-25             2.3                                                12        1-26             2.0                                                13        1-28             1.7                                                14        1-29             2.2                                                15        1-33             2.1                                                16        1-37             2.2                                                17        1-40             1.9                                                ______________________________________                                    

PREPARATION EXAMPLE 4

5.2 g of bis(p-diphenylamino)-1,3-diphenylpropane: ##STR25## wasdissolved in 52 ml of N,N-dimethylformamide, and 1.9 ml of phosphorousoxychloride was added thereto, and then the reaction was conducted at60° C. for 1 hour and 30 minutes.

The reaction solution was left to cool and then poured in 200 g of icewater, hydrolyzed with sodium hydroxide, and then subjected tofiltration and purification treatments by known methods to obtain 2.2 gof a monoformyl compound as a yellow oil and 2.9 g of a bisformylcompound as a yellow oil.

These compounds were found to be compounds of the following formulas,respectibly, from the following values of elemental analysis, the massspectrometric analysis and the infrared absorption spectrum analysis:

(1) Monoformyl compound

    ______________________________________                                        Elemental analysis:                                                           As C.sub.40 H.sub.34 ON.sub.2                                                            C %           H %    N %                                           ______________________________________                                        Calculated 85.99         6.13   5.01                                          Found      85.90         6.24   4.95                                          ______________________________________                                        Results of mass spectrometric analysis:                                       As C.sub.40 H.sub.34 ON.sub.2                                                 ______________________________________                                        MW = 558                                                                      M.sup.+  = 558                                                                 ##STR26##                                                                    ______________________________________                                    

(2) Diformyl compound

    ______________________________________                                        Elemental analysis:                                                           As C.sub.41 H.sub.34 O.sub.2 N.sub.2                                                     C %           H %    N %                                           ______________________________________                                        Calculated 83.93         5.84   4.77                                          Found      83.69         6.01   4.71                                          ______________________________________                                        Results of mass spectrometric analysis:                                       As C.sub.41 H.sub.34 O.sub.2 N.sub.2                                          ______________________________________                                        MW = 586                                                                      M.sup.+  = 586                                                                 ##STR27##                                                                    ______________________________________                                    

PREPARATION EXAMPLE 5

2.2 g of monoformyl compound synthesized in Preparation Example 4 and1.5 g of 1,1-diphenylhydrazine were reacted in the presence of an aceticacid catalyst in a mixed solution of 13 ml of tetrahydrofuran and 6 mlof methanol at room temperature for 12 hours.

Then, the reaction solution was poured in 500 ml of methanol andsubjected to filtration and purification treatments by known methods toobtain 1.7 g of yellow crystals (melting point: 67°-68° C.).

This compound was found to be a monohydrazone compound of the followingformula (Exemplary Compound No. 2-1as mentioned above) from thefollowing values of elemental analysis, the mass spectrometric analysisand the infrared absorption spectrum analysis:

    __________________________________________________________________________    Elemental analysis:                                                           As C.sub.52 H.sub.44 N.sub.4                                                               C %             H %                                                                              N %                                           __________________________________________________________________________           Calculated                                                                          86.15           6.12                                                                             7.73                                                 Found 86.01           6.35                                                                             7.61                                          __________________________________________________________________________    Results of mass spectrometric analysis:                                       As C.sub.52 H.sub.44 N.sub.4                                                  __________________________________________________________________________    MW = 724                                                                      M.sup.+  = 724                                                                 ##STR28##                                                                    __________________________________________________________________________

PREPARATION EXAMPLE 6

2.9 g of the diformyl compound synthesized in Preparation Example 4 wasreacted with 3.6 g of 1,1-diphenylhydrazine in the presence of an aceticacid catalyst in a mixed solution of 17 ml of tetrahydrofuran and 16 mlof methanol at room temperature for 12 hours.

Then, the reaction solution was poured in 500 ml of methanol and furthersubjected to filtration and purification treatments by known methods toobtain 3.6 g of yellow crystals (melting point: 205°-205.5° C.).

This compound was found to be a dihydrazone compound of the followingformula (Exemplary Compound No. 2-14 as mentioned above) from thefollowing values of elemental analysis and the infrared absorptionspectrum analysis (FIG. 4):

    ______________________________________                                        Elemental analysis:                                                           As C.sub.65 H.sub.54 N.sub.6                                                             C %           H %    N %                                           ______________________________________                                        Calculated 84.94         5.92   9.14                                          Found      85.04         5.90   9.03                                          ______________________________________                                         ##STR29##                                                                    ______________________________________                                    

EXAMPLE 18

1.0 part of titanium oxyphthalocyanine dye and 0.5 part ofpolyvinylbutyral (tradename: Polyvinylbutyral #6000, manufactured byDenki Kagaku Kogyo K. K.) were dispersed and pulverized in 30 parts of4-methoxy-4-methylpentanone-2 (manufactured by Mitsubishi KaseiCorporation).

This dispersion was coated by a wire bar on an aluminium layervapor-deposited on a polyester film having a thickness of 100 μm so thatthe weight after drying would be 0.2 g/m², followed by drying to form acarrier generation layer.

A coating solution prepared by dissolving 70 parts of the hydrazonecompound prepared in Preparation Example 6 and 100 parts of apolycarbonate as shown below in 900 parts of dioxane, was coated thereonand dried to form a carrier transport layer having a thickness of 17 μm.##STR30##

With respect to the electrophotographic photoreceptor having aphotosensitive layer comprising two layers thus obtained, thesensitivity i.e. the half-decay exposure intensity was measured andfound to be 2.8 (μW/cm²)⁻¹.

Here, the half-decay exposure intensity was determined by firstlycharging the photoreceptor in a dark place with corona discharge at -4.8KV, then subjecting it to exposure to a light of 775 nm, and measuringthe exposure intensity required until the surface potential decayed from500 V to 250 V.

EXAMPLE 19

A photoreceptor was produced in the same manner as in Example 1 exceptthat an unsymmetrical disazo dye of the following formula was usedinstead of the phthalocyanine dye used in Example 1. This photoreceptorwas subjected to exposure to incandescent light, and the half-decayexposure intensity was measured and found to be 1.0 lux.sec. ##STR31##

EXAMPLES 20 TO 25

Electrophotographic photoreceptors were produced in the same manner asin Example 18 except that hydrazone compounds as shown in Table 2,synthesized in the same manner as in Preparation Example 5 or 6, wereused instead of the hydrazone compound used in Example 18 and thetitanium oxyphthalocyanine dye used in Example 18 was used for thecarrier generation layer, and their sensitivities are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                                   Sensitivity                                        Example   Exemplary Compound No.                                                                         (μW/cm.sup.2).sup.-1                            ______________________________________                                        20        2-1              2.1                                                21        2-3              2.0                                                22        2-12             1.7                                                23        2-15             2.3                                                24        2-19             1.3                                                25        2-25             1.6                                                ______________________________________                                    

PREPARATION EXAMPLE 7

2.5 g of bis[m-N,N-diethylamino)phenoxy]methane as shown below wasdissolved in 52 ml of N,N-dimethylformamide, and 1.7 ml of phosphorousoxychloride was added thereto, and then the reaction was conducted at60° C. for 4 hours. ##STR32##

The reaction solution was left to cool and then poured in 200 g of icewater, hydrolyzed with sodium hydroxide, and then subjected tofiltration and purification treatments by known methods to obtain 2.5 gof a bisformyl compound as a yellow solid.

This compound was found to be a compound of the following formula fromthe following values of elemental analysis, the mass spectrometricanalysis and the infrared absorption spectrum analysis:

    ______________________________________                                        Elemental analysis:                                                           As C.sub.23 H.sub.30 N.sub.2 O.sub.4                                                     C %           H %    N %                                           ______________________________________                                        Calculated 69.32         7.59   7.03                                          Found      69.23         7.71   7.13                                          ______________________________________                                        Results of mass spectrometric analysis:                                       As C.sub.23 H.sub.30 N.sub.2 O.sub.4                                          ______________________________________                                        MW = 398                                                                      M.sup.+  = 398                                                                 ##STR33##                                                                    ______________________________________                                    

PREPARATION EXAMPLE 8

2.5 g of diformyl compound synthesized in Preparation Example 7 wasreacted with 3.2 g of 1,1-diphenylhydrazine in the presence of an aceticacid catalyst in a mixed solution of 30 ml of tetrahydrofuran and 30 mlof methanol at room temperature for 12 hours.

Then, the reaction solution was poured in 500 ml of methanol and furthersubjected to filtration and purification treatments by known methods toobtain 2.9 g of yellow crystals (melting point: 195° C.).

This compound was found to be a dihydrazone compound of the formula ofExemplary Compound No. 3-1 as mentioned above from the following valuesof elemental analysis, the mass spectrometric analysis and the infraredabsorption spectrum analysis (FIG. 5):

    ______________________________________                                        Elemental analysis:                                                           As C.sub.47 H.sub.50 N.sub.6 O.sub.2                                                     C %           H %    N %                                           ______________________________________                                        Calculated 77.23         6.89   11.50                                         Found      77.15         6.97   11.59                                         ______________________________________                                         Results of mass spectrometric analysis:                                      As C.sub.47 H.sub.50 N.sub.6 O.sub.2                                          ______________________________________                                        MW = 730                                                                      M.sup.+  = 730                                                                ______________________________________                                    

EXAMPLE 26

1.0 part of titanium oxyphthalocyanine dye and 0.5 part ofpolyvinylbutyral (tradename: Polyvinylbutyral #6000, manufactured byDenki Kagaku Kogyo K. K.) were dispersed and pulverized in 30 parts of4-methoxy-4-methylpentanone-2 (manufactured by Mitsubishi KaseiCorporation).

This dispersion was coated by a wire bar on an aluminium layervapor-deposited on a polyester film having a thickness of 100 μm so thatthe weight after drying would be 0.2 g/m², followed by drying to form acarrier generation layer.

A coating solution prepared by dissolving 70 parts of the hydrazonecompound prepared in Preparation Example 8 and 100 parts ofpolycarbonate resin as shown below (molecular weight: about 10,000 to40,000) in 900 parts of dioxane, was coated thereon and dried to form acarrier transport layer having a thickness of 17 μm. ##STR34##

With respect to the electrophotographic photoreceptor having aphotosensitive layer comprising two layers thus obtained, thesensitivity i.e. the half-decay exposure intensity was measured andfound to be 2.0 (μW/cm²)⁻¹.

Here, the half-decay exposure intensity was determined by firstlycharging the photoreceptor in a dark place with corona discharge at -4.8KV, then subjecting to exposure to a light of 775 nm, and measuring theexposure intensity required until the surface potential decayed from 500V to 250 V.

EXAMPLE 27

A photoreceptor was produced in the same manner as in Example 26 exceptthat an unsymmetrical disazo dye of the following formula was usedinstead of the phthalocyanine dye used in Example 26. The photoreceptorwas exposed to incandescent light, and the half-decay exposure intensitywas measured to be 1.5 lux.sec. ##STR35##

EXAMPLES 28 TO 36

Electrophotographic photoreceptors were produced in the same manner asin Example 26 except that dihydrazone compounds as shown in thefollowing Table 3, synthesized in the same manner as in PreparationExample 8, were used instead of the hydrazone compound used in Example26, and the titanium oxyphthalocyanine dye used in Example 26 was usedfor the carrier generation layer, and their sensitivities are shown inTable 3.

                  TABLE 3                                                         ______________________________________                                                                   Sensitivity                                        Example   Exemplary Compound No.                                                                         (μW/cm.sup.2).sup.-1                            ______________________________________                                        28        3-1              2.0                                                29        3-2              2.1                                                30        3-4              1.8                                                31        3-7              2.1                                                32        3-8              2.3                                                33         3-12            1.6                                                34         3-14            1.9                                                35         3-15            1.7                                                36         3-19            1.7                                                ______________________________________                                    

We claim:
 1. An electrophotographic photoreceptor comprising anelectrically conductive support and a photosensitive layer formedthereon, wherein said photosensitive layer contains at least one memberselected from the group consisting of hydrazone compounds of theformulas (I), (II) and (III): ##STR36## wherein X is a hydrogen atom ora group of the formula (IV):

    --C(R.sup.8)═N--Q.sup.2                                (IV)

Q¹ is a group of the formula (V), (VI), (VII), (VIII) or (IX); Q² is agroup of the formula (VI), (VII), (VIII), (IX) or (X); each of Q³ and Q⁴which may be the same or different, is a group of the formula (VI),(VII), (VIII), (IX) or (XI): ##STR37## Y is a bivalent hydrocarbon groupwhich may have substituents, A is an aliphatic linking group which mayhave substituents, where the main chain of the linking group may containan oxygen atom or a carbon-carbon double bond; in the case where themain chain of the linking group is composed of only carbon atoms, theconstituting carbon number is from 3 to 5; and in the case where theoxygen atom is contained, the constituting carbon-carbon chain lengthhas the carbon number of from 2 to 5; each of Ar¹ and Ar² which may bethe same or different, is an aryl group which may have substituents or aheterocyclic group; each of R¹, R², R³, R⁴, R⁵, R⁹, R¹⁵, R¹⁶ and R¹⁹which may be the same or different, is a hydrogen atom, a lower alkylgroup which may have substituents, a halogen atom or a lower alkoxygroup which may have substituents; each of R⁶, R⁸, R¹⁷ and R¹⁸ which maybe the same or different, is a hydrogen atom, a methyl group or a phenylgroup which may have substituents; each of R⁷ and R¹⁰ is an aryl groupwhich may have substituents in the formula (I), or an aryl group whichmay have substituents or a heterocyclic group in the formula (II); eachof R¹¹, R¹², R¹³ and R¹⁴ which may be the same or different, is an alkylgroup which may have substituents, an aralkyl group which may havesubstituents; an aryl group which may have substituents, a vinyl groupwhich may have substituents, or an allyl group; and R²⁰ is an aryl groupwhich may have substituents, or a heterocyclic group.
 2. Theelectrophotographic photoreceptor according to claim 1, wherein thephotosensitive layer contains the hydrazone compound of the formula (I).3. The electrophotographic photoreceptor according to claim 1, whereinthe photosensitive layer contains the hydrazone compound of the formula(II).
 4. The electrophotographic photoreceptor according to claim 1,wherein the photosensitive compound contains the hydrazone compound ofthe formula (III).
 5. The electrophotographic photoreceptor according toclaim 1, wherein the photosensitive layer comprises a carrier generationlayer and a carrier transport layer contains at least one memberselected from the group consisting of the hydrazone compounds of theformulas (I), (II) and (III).
 6. The electrophotographic photoreceptoraccording to claim 5, wherein the carrier transport layer contains atleast one member selected from the group consisting of the hydrazonecompounds of the formulas (I), (II) and (III), and a binder.
 7. Theelectrophotographic photoreceptor according to claim 1, wherein thephotosensitive layer contains photoconductive particles capable ofgenerating an electric charge carrier and at least one member selectedfrom the group consisting of the hydrazone compounds of the formulas(I), (II) and (III), which are added in a binder.
 8. Theelectrophotographic photoreceptor according to claim 2, wherein X is ahydrogen atom.
 9. The electrophotographic photoreceptor according toclaim 2, wherein X is a group of the formula (IV).
 10. Theelectrophotographic photoreceptor according to claim 3, wherein X is ahydrogen atom.
 11. The electrophotographic photoreceptor according toclaim 3, wherein X is a group of the formula (IV).
 12. Theelectrophotographic photoreceptor according to claim 4, wherein X is ahydrogen atom.
 13. The electrophotographic photoreceptor according toclaim 4, wherein X is a group of the formula (IV).